[lfm]

Originally Posted by CADavis

http://mersenne-aries.sili.net/digits.php calculate number of digits from an exponent

i think it something above 332,000,000 for the exponent to give a 100M digit mersenne number.

Its pretty easy if you have a proper calculator. Just 1e6*ln(10)/ln(2)=3321928.09 or so.